Mr. Weinkle

Life Science

Light Microscope Lab 1

Write a lab report to earn a grade. Lab procedure is worth 50%; finished report is worth 50%. Your writing should be clear and detailed. You should include drawings for full credit.

Purpose:

·        To learn the nomenclature and use of compound light microscope.

·        To construct a practice slide using threads.

·        To learn to view the 3-dimensional specimen with the microscope.

·        To learn to use the various magnifications and controls.

·        To prepare and use wet and dry slides.

·        To draw and describe specimens.

No hypothesis or prediction required.

Materials:

Compound light microscope, handouts, blank glass slides, prepared slides, droppers, paper towels, pencils for drawing (no pens), colored pencils, blank paper.

Procedure:

Study the handout for this exercise and compare the drawing with the actual microscope. Locate and name each part on the microscope. Label the drawing.

When using a compound light microscope, ALWAYS start with the LOW magnification objective. On higher magnifications be careful NOT to crush the slides or put the lens in water. On all views be sure to write down the magnifications and the slide you're using. Describe the sample in detail. Look very carefully and take your time, make drawings. Use your textbook and available reference books to help you to identify these structures.

Part 1- Making a practice Slide

Tape 2 threads of different colors to the upper surface of a plain slide. Cross the 2 threads to for 1 intersection and tape the threads down on the opposite side of the upper surface. Look at the image under several different magnifications. (See above illustration).  Practice focusing with the gross and fine focus dials. Change the diaphragm settings to see how the view is affected.

Part 2: Observing living specimens and prepared slides

1.      Put ONE drop of water from each water sample on the slide and look for activity. Draw and describe any organisms you see. Use at least 2 magnifications and 2 diaphragm openings. Draw several (a minimum of two) organisms for later identification. Draw them larger than life. Look for as much detail as you can see and record each detail in writing.

2.      Use at least 2 prepared slides and observe the specimens. Use a minimum of 2 prepared slides per team (more if time permits). Be sure to identify the specimen and record it with your observations. Return these slides intact when you have completed observing at various magnifications.

3.      Clean and dry all slides and coverslips before returning them (when you have completed observations). Clean the microscope stage before returning the microscope to the main podium. All team members help with cleanup: Scopes and slides returned to podium clean and dry, ALL waste paper and trash must be put in the trash bin, all tables wiped and dried.

4.      All team members must produce a lab report.

Note: Each team is responsible for the proper care and use of lab materials.

Results and discussion:

Include your drawings.

Your lab report should include all drawings and labels. Include all observations. The final report should include a cover sheet and all required sections clearly labeled.

Answer these questions:

1.      Which magnifications offered you the best view of the specimens? Which aperture sizes offered you the best view?

2.      What living organisms did you observe? What features can you use to identify them?

Conclusions:

What was the most interesting part of this lab investigation? How would you improve it?  Did you look at anything without being told? Describe what you saw. Did you learn anything- explain what it was.

COMPOUND LIGHT MICROSCOPE DIAGRAM

Label each part indicated by the arrows:

1.       Arm - this attaches the eyepiece and body tube to the base.

2.       Base - this supports the microscope.

3.       Body tube - the tube that supports the eyepiece.

4.       Eyepiece - where you place your eye.

5.       Coarse focus adjustment - a knob that makes large adjustments to the focus.

6.       Fine focus adjustment - makes fine adjustments to the focus, smaller than the coarse focus knob.

7.       Diaphragm - an adjustable dial under the stage, allowing different amounts of light onto the stage.

8.       High-power objective - provides about 400 powers.

9.       Medium power objective - provides about 100 power

10.   Low-power objective - provides about 40 powers.

11.   Light source - this directs light upwards onto the slide.

12.   Revolving nosepiece - the rotating device that holds the objective lenses.

13.   Stage - the platform on which a slide is placed.

14.   Stage clips - metal clips that hold a slide securely onto the stage

15.   Power switch- turns on the light source.

16.   Power cord- supplies electricity to the light source.

Note: The illustration is free for classroom use.